As smart phones are introduced and a variety of devices using a network increases rapidly, traffic throughput of a mobile communication network gradually reaches its limit. In this case, efforts are underway to reduce overload of the network using a detour.
For example, a 3rd Generation Partnership Project (3GPP) standardization group provides a solution for offloading traffic to a core network using a small cell (or a femtocell) adopted to increase cell capacity and to address a shadow area. That is, 3GPP defines a Selective IP Traffic Offload (CSIPTO) function allowing a User Equipment (UE) to use a nearby Packet Data Network (PDN) Gateway (GW) for Internet access. The CSIPTO achieves use of a shorter path to Internet, but it can also cause a problem of Internet Protocol (IP) session continuity. When the UE needs to change the GW, a flow anchored on a nearby GW (e.g., a GW in a local network) can break. The UE may need to change the GW due to its mobility. When the UE leaves a coverage area of the GW and enters a coverage area of another GW, the network can direct the GW change.
When the GW is close to the UE, it may have to change more frequently due to the mobility of the UE. When the GW is changed in the middle of a flow and the flow requires IP session continuity (e.g., a VoIP calls or a real-time video stream), the GW change can change an IP address which causes a breakage of an ongoing IP session.
Meanwhile, in order to cancel disadvantages in using a local GW, the UE need to seek for better timing and coordination of the GW change. More specifically, when the UE has a flow requiring the IP session continuity, the GW change may not be executed. 3GPP does not allow the network to blindly conduct the GW change, and the network needs to consult with the UE prior to the GW change.
Secondly, the UE can use a higher-level protocol having mobility management. For example, SIP-based flows can use SIP mobility. The SIP mobility is an end-to-end mobility protocol which can change an end-point IP address of the session through end-to-end signaling.
At the time of the GW change, when a SIP client is provided with a new IP address from a new GW while still retaining an IP address obtained from a previous GW, the flow can be switched from the previous IP address to the new IP address without service interruption by updating the end-point IP address and utilizing it as much as possible. Such a procedure requires availability of both of the previous and new GWs connected to the same PDN at the same time. However, a current standard allows activating the new GW only after the previous GW is released when both of the GWs are connected to the same PDN (as indicated by an Access Point Name (APN)).
Thus, during a transition period (until higher-layer protocols converge), a new technology for allowing using the new GW and the previous GW is demanded. SIP is given as an example of the higher-layer protocol having its own mobility management scheme. Besides, there is a plurality of other higher-layer protocols such as Stream Control Transmission Protocol (SCTP), Multipath TCP (MPTCP), mobile IP, and application specific protocols (e.g., various instant messengers).
A various embodiments of the present invention may provide a network device for supporting gateway change in a mobile communication system, and an operating method thereof.